The instant invention is directed to the manufacture of a silicon on insulator (SOI) wafer, and more particularly to a method of producing an SOI wafer having a buried oxide layer at a lower cost and which is also more reliable than conventionally known wafers. According to the method of the invention, such an SOI wafer can be produced using standard equipment in a normal production facility.
SOI wafers having buried oxide layers are an attractive technology for deep-submicron CMOS and radiation-hardened devices because the buried oxide layer offers both device isolation and the ability to getter defects, such as oxygen and metallic ions, away from the operating region of the device.
There are generally two conventional methods for producing SOI wafers. The first is SIBOND. With SIBOND wafers, as illustrated in FIG. 1A, an oxide layer 12 is formed on the surface of a substrate 10. A second silicon wafer 14 is bonded to the top surface of the oxide layer 12. Using this method, the top wafer 14 must be formed relatively thin so that the oxide layer 12 is at the desired depth to achieve the device isolation. This results, in an increased potential for defects as the thin layer is worked. Another drawback to the SIBOND wafer is manufacturing cost. Moreover, due to the complexity of the manufacturing process, the SOI wafer cannot be incorporated into the "in-house" production of a semiconductor device. Instead, the SOI wafer must be purchased from an outside source.
The second method employed to produce SOI wafers is SIMOX (i.e., Separation by Implanted Oxygen). In SIMOX technology, as illustrate in FIG. 1B, oxygen 16 is implanted into the substrate 10 at relatively low energies to form the buried oxide layer 13. As with SIBOND, one drawback for a semiconductor device manufacturer who wishes to use conventional SIMOX wafers is that the equipment need to produce such wafers is not of the type normally used in manufacturing semiconductor devices. Thus, typically SIMOX wafers must also be purchased from an outside source. Accordingly the costs of using SOI wafers is increased.
Another drawback associated with SIMOX wafers arises from the Oxygen implantation process itself. The oxygen implantation is carried out at relatively low energy levels, which tends to form defect regions in the surface of the wafer down to the buried oxide layer 13 through portion 15 of the substrate 10. Moreover, SIMOX wafers are typically considered "dirty", in the sense that significant amounts of iron impurities are introduced into the wafer during oxygen implantation. Since oxygen is not a standard species for ion implantation, the implanting device must be configured in a way which introduces these unwanted impurities. One of the downsides of using SIMOX wafers is that the iron rich nature of the wafer will significantly hinder the production and/or operation of most semiconductor devices. Moreover, the oxygen implantation step is not practical for implementation in standard device production facilities as part of the manufacturing process.
Accordingly it is an object of the instant invention to produce an SOI wafer which includes a buried oxide layer but which can be made using the type of equipment typically used by semiconductor manufacturers and to reduce the costs associated with making and using SOI wafers.
Another object of the instant invention is to provide a method for producing SOI or SOI like wafers which can be implemented in standard semiconductor device manufacturing processes.
Still another object of the instant invention is to produce an SOI wafer which is more reliable and does not have the undesirable impurities associated with the conventional SOI wafers.